Evaluation of the IRI model using CHAMP observations in polar and equatorial regions

Liu, Huixin; Stolle, Claudia; Watanabe, Shigeto; Abe, Takumi; Rother, M.; Cooke, D. L.

doi:10.1016/j.asr.2006.08.006

Cited by 27 publications

(20 citation statements)

References 17 publications

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“…Similar phenomenon was found to occur at Port Lockroy (65.8°S, 63.5°W) [ Rastogi , 1960] and also in the northern hemisphere at Millstone Hill (42.6°N, 71.5°W) [ Evans , 1965]. Global observations from the CHAMP satellite showed unusual diurnal variations of Ne in summer midlatitudes in both hemispheres [ Liu et al , 2007b]. Recently, detailed climatology of the WSA has been reported based on modern satellite observations [ Horvath and Lovell , 2009; Lin et al , 2009; Jee et al , 2009; He et al , 2009, and references therein].…”

Section: Introductionsupporting

confidence: 66%

Phase reversal of the diurnal cycle in the midlatitude ionosphere

2010

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[1] The typical diurnal cycle of the midlatitude F region electron density consists of a midday maximum and a midnight minimum. However, a phase reversal of this diurnal cycle has been found to occur in three distinct regions on the globe. They are the East Asian (EA) region centered around (53°N, 150°E), the Northern Atlantic (NA) region centered around (45°N, 50°W) and the South Pacific (SP) region centered around (60°S, 110°W). The intensively reported Weddell Sea Anomaly falls inside the SP region. The phase reversal occurs during March-August in EA and NA regions, and between August and March in SP region, being most prominent in local summer. Furthermore, this diurnal anomaly is more pronounced at solar minimum than at solar maximum, and more pronounced in SP region than in NA and EA regions, in terms of larger diurnal magnitude and more months it lasts in a year. It is emphasized that the diurnal anomaly consists of not only a nighttime enhancement, but also a concurrent noontime depletion. Hence, midlatitude summer nighttime enhancements reported in previous studies are just part of this reversed diurnal cycle. The cause for the phase reversal involves several interplaying physical processes. Among these, the neutral wind combined with the geomagnetic field configuration plays a pivotal role. It generates a one-wave longitudinal pattern at southern middle latitudes and a two-wave pattern at northern middle latitudes, whose wave peaks correspond to the center of the SP, EA, and NA regions, respectively. The seasonal variation of neutral winds and downward motion of the ionization induced by thermal contraction of the ionosphere at sunset may largely control the occurring local time of the nighttime density enhancement and how long it persists in different months. The phase reversal occurs as a result of close ion-neutral coupling. It is further noted that winter anomaly in the EA, NA, and SP regions is very weak or missing.Citation: Liu, H., S. V. Thampi, and M. Yamamoto (2010), Phase reversal of the diurnal cycle in the midlatitude ionosphere,

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Section: Introductionsupporting

confidence: 66%

Phase reversal of the diurnal cycle in the midlatitude ionosphere

2010

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“…A comparison between the IRI 2001 model and data from the CHAMP satellite showed general agreement between CHAMP data and the IRI model in the seasonal variation of the electron density and temperature, with some exceptions (Liu et al 2007). A later study performed a comparison with Slant Total Electron Content (STEC) data and found that IRI2007 is much improved compared to IRI2001 (Coïsson et al 2008).…”

Section: Stec From Pre-computed Ionospheric Datamentioning

confidence: 93%

A Review of Higher Order Ionospheric Refraction Effects on Dual Frequency GPS

et al. 2010

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Higher order ionospheric effects are increasingly relevant as precision requirements on GPS data and products increase. The refractive index of the ionosphere is affected by its electron content and the magnetic field of the Earth, so the carrier phase of the GPS L1 and L2 signals is advanced and the modulated code delayed. Due to system design the polarisation is unaffected. Most of the effect is removed by expanding the refractive index as a series and eliminating the first term with a linear combination of the two signals. However, the higher order terms remain. Furthermore, transiting gradients in refractive index at a non-perpendicular angle causes signal bending. In addition to the initial geometric bending term, another term allows for the difference that the curvature makes in electron content along each signal. Varying approximations have been made for practical implementation, mainly to avoid the need for a vertical profile of electron density. The magnetic field may be modelled as a tilted co-centric dipole, or using more realistic models such as the International Geomagnetic Reference Field. The largest effect is from the second term in the expansion of the refractive index. Up to several cm on L2, it particularly affects z-translation, and satellite orbits and clocks in a global network of GPS stations. The third term is at the level of the errors in modelling the second order term, while the bending terms appear to be absorbed by tropospheric parameters. Modelling improvements are possible, and three frequency transmissions will allow new possibilities.

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“…The root mean square (RMS) difference of electron density was about 10 3 cm À3 above 150 km for the horizontally stratified ionosphere (Schreiner et al, 2007). In addition, CHAMP uses a planar Langmuir probe (PLP) to perform in situ measurements of ionospheric electron density and temperature every 15 s. The accuracy of the PLP measurements is within 10% (Liu et al, 2007).…”

Section: Datamentioning

confidence: 99%